This invention relates to chairs that are adjustable for the comfort of the user. In particular, this invention relates to chairs such as are suitable for use in an office environment and in which the angle of the back rest relative to the seat rest can be easily adjusted by the user for his or her individual comfort.
It is known that the efficiency and productivity of office workers is dependent in part on their physical comfort. An important aspect of physical comfort is chairs that can be adjusted to suit the needs of a particular user. Designing office chairs for this purpose can be challenging, because each chair must be adjustable to accommodate users of many different heights and weights. The chair also should be adjustable to accommodate a variety of different seating postures. In particular, it is frequently desirable for a chair back rest to recline from the upright position in a manner adjustable by each user. Some prior art chairs having reclining seat backs exert a shear force on the user's back when reclining in the chair; this shear force can be so great that it causes the user's shirt to be pulled out of place. It would be desirable for a seat back of a chair to be able to recline without creating an uncomfortable amount of shear against the user's back. Further, the adjustment of the reclining angle should be independent of the height adjustment of the seat, or of any other adjustments.
U.S. Pat. No. 1,501,181 discloses an office chair having a reclining back rest by means of a pivoting supporting arm, and having a spring that provides a counterforce.
U.S. Pat. No. 2,105,510 discloses a chair having a back rest that can be inclined by releasing and tightening wing nuts on bolts, and having a spring for controlling the tension of the back rest.
U.S. Pat. No. 2,211,090 discloses an office chair with a reclining back, the back being pivotably connected to a mounting member which is in turn pivotably mounted on the chair spindle.
U.S. Pat. No. 2,410,871 discloses a chair having a back support including a spring that is retained in position by cups at either of its ends.
U.S. Pat. No. 2,680,474 discloses a chair having a back rest connected to an arm that pivots about a pivot rod, the rotation of the pivot rod being controlled by stops.
U.S. Pat. No. 2,770,292 discloses an office chair with a spring mounted back, the back support being pivotally mounted to the chair seat, the spring providing yieldingly opposing rearward swinging of the back from a normal position, and wherein the spring-mounted back can be adjusted forwardly and rearwardly with respect to the chair seat.
U.S. Pat. No. 3,441,311 discloses a chair control in which the spring mechanism that resists the tilting action of the chair seat or back is mounted perpendicular to the pivotally connected frame members.
U.S. Pat. No. 5,452,937 discloses a chair having a reclining chair back, which chair back is mounted on an arm attached to a pivot point under seat and having a spring that applies a counterforce to the pivoting action.
U.S. Pat. No. 5,658,045 discloses a chair having a mechanism for synchronous adjustment of the seat and backrest. The position is maintained by a catch mechanism which is released by operation of an actuation lever.
U.S. Pat. No. D460,870 is a design of an office chair.
U.S. Pat. No. 6,213,552 discloses an office chair in which the angle of the back is adjusted synchronously with the angle of the seat.
U.S. Pat. No. 6,276,755 discloses as prior art an office chair having a back on a back support that inclines with respect to the chair seat.
U.S. patent application Publication No. US 2002/0043845 A1 discloses a chair having a spring and a preload member, and discloses a method of installing the spring.
U.S. patent application Publication No. US 2003/0075961 A1 discloses an office chair having a track by which the seat part can move forward and upward or downward and rearward, and having a swivel device.
It is thus one object of the invention to provide a chair with a tiltable back rest.
It is another object of the invention to provide a chair with a tiltable back rest which is comfortable for the user and which does not result in excessive shear force on the user's back when the user exerts force against the backrest so as to cause it to recline.
It is still another object of the invention to provide a chair with a tiltable back rest which is comfortable for the user and which does not result in excessive shear force on the user's back when the user exerts force against the backrest so as to cause it to recline, and which is of relatively simple design.
It is yet another object of the invention to provide a chair with a tiltable back rest which is comfortable for the user and which does not result in excessive shear force on the user's back when the user exerts force against the backrest so as to cause it to recline, and which is of relatively simple design, and which can be locked so as to maintain the back rest in the upright position.